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TOP 10 ANIMAL GROSS-OUTS : Koala

5. KOALA

How gross could these Australian natives get when they spend up to 22 hours a day sleeping? Answer: plenty. The koala's diet depends solely on eucalyptus leaves, which are packed with toxins. Fortunately, the koala's digestive system contains special bacteria that detoxify the leaves. Their babies, however, are not born with this same mechanism, but they learn how to build up their defense system by eating their mother’s meal ... the second time around. That's certainly an interesting way to deliver a vaccine!